Yep! No problem. Hope it all works well. :zbeer::zbeer:
Andrew
I am not sure of the full properties of Polyester in relation to its absorption into the surface of the cedar. Please think ahead when advancing this project. What are you going to fix the deck to the hull with. Polyester? I dont think so. What about the keel box to the hull and the other reinforcements inside. Don’t spoil it for the sake of saving a few bucks. I think that Polyester is quite a bit heavier than epoxy and think of the long lasting smell.
I would go with Epoxy.
Ralph
Ralph,
Could I not use epoxy to glue the pieces together? I am asking the questions here before going any further so as not to ruin what has been done so far.
Andrew
Please re-read my earlier post.
Epoxy is a glue/adhesive. It is a finishing resin that seals wood from water or rot. It can be mixed with other products tochange it color, look of physical properties.
Polyester resin is only good for one thing - to lay up layers of fiberglass cloth. You cannot glue it. On some wood surfaces it won’t adhere. It smells. Methyl Ethyl Keytone (MEK) is used to chemically harden the polyester resin, but you are using “drops” of MEK for polyester as compared to measurable ounces of hardner for epoxy. I don’t know of any developed and accurate dispensing system for polyester hardner - so expect varying times of cure. (Neigbor didn’t heed my epoxy suggestion and had 7 coffee cans with brushes stuck in them when working on his big boat. They cured too fast and on top was a waste of money). Polyester tends to cure hard and a it brittle, while mose marine epoxies tend to stay just a little bit softer allowing for a bit of stretch befor e breaking. Polyester will fail at the glass level, while epoxy (if it fails) does so within the wood cell structure. Both are chemicals and fire, flame, and proper safety practices are always recommended.
Probably - (just a guess) you have some autobody repair resin which isn’t formulated for wood adhesion.
All of the above can be minute issues - or fairly large ones. Personally, after putting in time and effort to build a model boat, I would hate to see something mess up all my time and hard work. Not saying it can’t happen with epoxy, but I personally (since 1978) would trust myself using epoxy over polyester resin any day.
Have you visited any of the epoxy manufacturer’s sites to read their technical information? There are plenty of companies out there making excellent products. Follow their instructions and you will be rewarded. And before you decide - ask yourself - “HOW COME?”
Why do big boat builders creating wooden boats, kayaks and canoes recommend and use epoxy, while solid fiberglass boat and bathtub builders using chopper guns, shredded glass fibers use polyester resin?
I would suggest each product has it’s best use - and when you are trying to make a product to sell and be strong, the builders have more or less set the standards.
That’s about the best argument I can make in favor of epoxy.
Do what you want - but keep in mind, several folks here, have given you the best advice that they can - and usually based on thier own experiences.
Dick,
Thank you, this is why I posted this on this forum, to find out what other people are doing. I will use epoxy. The polyester does say it can be used on wood, to restore rot and to laminate glass.
Andrew
I may have got this wring, but I thought you had decided to use a very thin glass outer layer. Polyester is well known in this application, full size and elsewhere. Used on its own it is weaker and probably more brittle than epoxide. If all you are doing is putting on a sealing coat, neither of these is a serious consideration in my view. The cear is providing the strength and the resin (whatever it is) is helping keep the water out.
Weights. According to Netpolymer:
Matrix Density (g/cm3)
Epoxy 1.1-1.4
Polyester 1.2-1.5
so there is very little in it - the spread across one type is bigger than the difference between them.
As far as sticking the bits together is concerned, presumably you have done this BEFORE you apply a final sealing coat.
The water permeability of poyester is worse than that of epoxide, but given the time the average model yacht spends in the water this is hardly an issue: they are both pretty impermeable.
Cheers,
Bear in mind that epoxy will stick to polyester resin, but polyester resin will not stick to epoxy.
Happy Yachting - Kip
Thank you for the advice Angus and kip.
Andrew,
I would not use polyester on cedar. Polyester does not adhere well to some timbers (with “high” levels of natural resin? - WR cedar, most pines etc), and sometimes has difficulty curing when in contact with it (you sometimes can easily pull the set resin layup off the timber revealing a sticky surface). Wiping the timber before applying resin with acetone can help.
Epoxy is fine. Just coat both sides of your planked hull with epoxy, then fill/paint/more epoxy/… or whatever.
Jon
Given Jon’s comments, I think I revise my opinion on the desireability of using polyester. As Dick effectively points out (to me at least) polyester technology is now pretty old hat - I made my first polyester glass mouldings when I was anout 13 and that, I am horrified to tell you, was 43 years ago. Thirsty years ago, I was builing very lightweight 30 footers of polyster, glass, balsa with never a spray layup in sight. But more of that in a moment.
In those days there was a fashion for doing more or less what you are talking about with full size boats - using polyester since epoxides were quite prohibitively expensive for even the best funded yacht operations.
Generally the sheathing worked, but in some cases it did come off in sheets. I am not aware of any evidence that this was linked to any particular type of timber. In the mythology of the time it was put down to incorrect preparation/a damp substrate.
If you still want to try it, why not mix a little resin, paint it onto some scrap ceadar and see what happens? You mat some yourself some money or you may not. Once the thing is reasonably well cured (North American central heating should achieve this in a day or so), it hould be pretty apparent whether the thing is going to stick or not - the bond is purely meechanical and you either have it or you don’t. Help it by roughing up the suface a bit.
Incidentally, it is fascinating that, although I am these days a fanatical admirer of epoxides, in my heart of hearts, they are new-fangled, finikey, require care and precision in use and can do funny things … Polyesters and vinylesters are nice, familar things that you can feel at home with, pull put u with any amount of abuse, etc, etc.
I suspect that Dick got into these things after the Age of Polyester had ended and the Age of Epoxide had dawned. His feelings are the precise reverse. If you are familiar with them, you can get away with murder. For example, I would never have believed it, but my great glass guru ‘Our Roy’, demonstrated that polyester would go off quite satisfactorily with about 10% added water if it was well-stirred in before the resin was catalysed. :graduate:
:zbeer::zbeer::zbeer:
Hmmmm - “Age of Polyester” - I hope you speak of the resin - not my “Leisure Suit” days? 
Actually I started on my self-taught boat repair education in 1977. I had “borrowed” my brother-in-laws orange Prindle 16 catamaran ( my Sizzler was on the beach at my in-laws place) so I could race in a local beachcat regatta open only to Hobies and Prindles at the time. As we came towards shore, a very large piece of concrete floated out and in front of my boat. As I tried to “straddle it” with both hulls, it managed to place a fiberglass tear about 4 inches long and about 1 inch wide on the inside of one hull. All the way home I was wondering how best to patch it. I was convinced polyester auto body repair kit, covered with “Bondo” paste and then try to match the bright orange hull color was the way to go.
A good sailing friend at work suggested I try some WEST System stuff and I bought a quart/pint quantity. Found out how easy it was to lay up some glass and epoxy, then sand down and fill with epoxy and microballoon mixture. Sand and fair a bit more and prime with light gray primer. Then all the planets aligned, God shown down upon me, the angels sang, and a chance purchase of a can of spray paint called “Chevy Hugger Orange” and dang if it didn’t blend perfectly! In retrospect, I guess I was just damn lucky for the friend and the guessed at paint color.
Regardless - after spending some time and using the epoxy products more, I just shook my head when a different brother-in-law simply peeled the fiberglass skin off the hull of a plywood run-about of his dad’s. A full 9 oz. of glass cloth with polyester resin and it came off the plywood in big sheets. Looking back it might have been moisture migration from the inside of the hull trying to get out. At the time, we just guessed the mixture wasn’t right, or it was the wrong product. Haven’t been back to polyester as a resin since.
As for the “Age of Polyester” - it’s still hanging in the closet and comes out on very special occasions like Halloween or maybe a class reunion ! I’m just afraid of car trouble when wearing it in case a police officer stops to see if anything is wrong. Difficult to explain … like the time with the pig, the chicken, and the monkey… but that’s a different story ! :D:D
Well I glassed the hull yesturday. I did use epoxy, and was able to vacuum bag it. only pulled a little vac on -5. It came out great but probably heavy at 600kg for just the hull. I have see it posted with deck hull and fittings for 650kg so I better make a light deck. The cedar looks good but i am sorry i am going to paint it.
Andrew